Solvent for obtaining very high yields of aldehydic products from soybean oil



United States Patent 3,349,106 SOLVENT FOR OBTAINING VERY HIGH YIELDS 0F ALDEHYDIC PRODUCTS FROM SOYBEAN OIL Danny J. Moore, Peoria, lll., assiguor to the United States of America as represented by the Secretary of Agriculture N0 Drawing. Filed May 5, 1965, Ser. No. 453,526 2 Claims. (Cl. 260-406) ABSTRACT OF THE DISCLOSURE Substantially theoretical yields of methyl azelaaldehydate are obtained from methyl oleate by conducting both the ozonization thereof and the catalytic hydrogenolysis of the resulting ozonides in about two parts by weight of a reaction solvent consisting of about equal parts of a C -C monocarboxylic acid and a C -C aliphatic or cyclic alcohol, washing a methylene chloride or diethyl ether solution of the reaction products, and isolating the desired methyl azelaaldehydate therefrom by vacuum distillation.

An nonexclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to an improved process for obtaining essentially quantitative yields of w-formyl esters, i.e., aldehydic esters such as methyl azelaaldehydate by ozonolysis of unsaturated vegetable oil esters followed by catalytic hydrogenation of the ozonolysis products.

A major barrier to commercialization of processes for obtaining aldehydic products from unsaturated esters of vegetable oil acids, e.g., methyl oleate, by ozonolysis and catalytic hydrogenation of the ozonolysis products has been the very poor yields. Although Pryde et al., J. Org. Chem, 27: 3055 (1960), and US. Patent No. 3,112,329 teach that the addition of a minor proportion of pyridine to the methanol employed as solvent for the reduction of the ozonolysis products improved the yields of aldehydic. products, pyridine is toxic and has an ofiensive odor. Furthermore, the obtained improvement is not very substantial and still leaves much to be desired.

One objective of the present invention is a process for obtaining further improved and essentially theoretical yields of w-formyl esters such as methyl azelaaldehydate from the corresponding unsaturated fatty esters without the use of pyridine. Another object is a process which provides a much more efiicient catalytic reduction.

In accordance with the above objects I have now made the unobvious discovery that when a 50:50 molar mixture of a lower alcohol, such as n-butanol, and a carboxylic acid such as acetic acid, is used as the solvent for both the ozonolysis of the unsaturated fatty esters and also for the subsequent catalytic reduction of the ozonized intermediates, the yields of the desired aldehydic products are essentially theoretical. This discovery is surprising inasmuch as Helferich et al. Ber. 57B 1911 (1924), Noller et al., JACS, 48: 1074 (1926), and IP-ryde et al., ibid., 27: 3055 (1060), all show that in acetic acid the yields of methyl azelaaldehydate are only about 65 percent of theory whereas Pryde et al., ibid., 25: 618 (1960) show practically identical yields using n-butanol as the sole solvent for both phases of the reaction. Thus, it was unexpected that a mixture consisting of two rather inefficient solvents would cooperate in a synergistic manner to provide substantially quantitative yields of w-formyl ester.

Although acetic acid and n-butanol, respectively, are the preferred specie-s of carboxylic acid and alcohol of my improved ozonization and reduction solvent mixture, this preference is based on low cost and ready availability, and similarly improved yields are obtained by employing secondary alcohols such as secondary butyl alcohol or an aromatic alcohol such as benzyl alcohol for the n-butanol as Well as by substituting other aliphatic acids such as propionic acid or pelargonic acid for the acetic acid. The proportion by weight of solvent mixture to be used per unit weight of methyl oleate or homologous unsaturated fatty ester is not critical and will be in the range of about 2:1 to about 50:1. The following specific embodiments are intended to be illustrative rather than limiting.

Example 1 A reaction system consisting of a 1-liter round-bottom flask fitted with an ozone inlet, a condenser, and a stirrer was sequentially charged with 30.0 g. (0.1 mole) of methyl oleate wherein 91 percent of the unsaturation is at C and 5 percent thereof is at C glacial acetic acid, 250 g., and Z-methoxyethanol, 250 g.

After cooling the above mixture to 10 C., oxygen gas containing about 2.5 percent by weight of ozone was bubbled through the stirred reaction mixture until the cessation of ozone absorption at the expected value of 5.76 g. confirmed the absorption end-point. Then 0.6 g. of lO-percent palladium on carbon was introduced into the reactor and hydrogen was admitted at a rate of 300 liters per hour. The reaction temperature was maintained at 1520 C. and-the take-up of 'hydrogen ceased in 15 minutes. The catalyst was removed by filtration through diatomaceous earth, the solution neutralized with NaHCO then mixed in an equal volume of methylene chloride, the methylene chloride solution extracted with water to remove the 2-methoxyethanol and sodium acetate, the methylene chloride evaporated off, and distillation of the product at 66-70 C./0.09 mm. gave 16.6/g. of pure methyl azelaaldehydate correpsonding to a 97.0 percent yield.

Example 2 The reactor system of Example 1 was charged with 30.0 g. of methyl oleate identical with that of Example 1, 297 g. of n-butyl alcohol, and 242.4 g. of glacial acetic acid, and the mixture cooled to 4 C. The ozone-containing oxygen was bubbled through until 5.83 g. of ozone was absorbed. Catalytic reduction and work-up as in Example 1 gave a 98 percent yield of methyl azelaaldehydate.

However, in a parallel experiment wherein diethyl ether was substituted for the methylene chloride and the water-extracted ethereal layer then freed of water with Drierite, the dehydrating agent caused extensive acetal formation, the 21.39 g. of product consisting of 10.88 g. of pure methyl azelaaldehydate (63.3 percent of theory), 10.3 g. of methyl-9,9-dibutoxynonanoate (37.7 percent of theory), and 0.21 g. of methyl-8-carbobutoxynonanoate (1 percent of theory), thus representing an overall 99 percent conversion of double bonds to carbonyl. The presence of the corresponding aoetal, i.e., methyl-9,9-din-butoxynonanoate does not interfere with the utility of the methyl azel-aaldehydate inasmuch as reactions involving w-formyl ester starting materials commonly form acetals therefrom.

Example 3 Methyl oleate, 30.0 g., dissolved in a mixture of 40.7 g. n-propyl alcohol and 44.3 g. of glacial acetic acid, all present in a reaction apparatus identical to that of Example 1 excepting that the flask had a capacity of 250 ml., was subjected to ozonization until 5.75 g. of ozone had been absorbed. After catalytically reducing the ozonized material as in Example 1, the neutralized filtrate was dissolved in an equal volume of diethyl ether, the ethereal solution Washed with several changes of water, and the 16.82 g. (97 percentof theory) of highly pure methyl azelaaldehydate was obtained by vacuum distillation of the undried ethereal solution.

Example 4 Example 5 Example 4 was repeated excepting that 5.06 g. of methyl oleate was used, 5.75 g. of cyclohexyl alcohol was substituted .for the benzylalcohol, 4.25 g. of propionic acid was used, and the temperature during both ozonization and reduction was held at 2 C. Vacuum distillation of the ethereal layer yielded 2.66 g. of methyl azelaaldehydate (92 percent of theory).

Example 6 Methyl oleate, 5.63 g., ethyl alcohol, 39.2 g., and acetic acid, 50.8 g., were treated as in Example 4. Vacuum distillation provided 3.13 g. of methyl azelaaldehydate corresponding to a theoretical yield of 97 percent.

Example 7 Methyl oleate, 5.04 g., glacial acetic acid, 3.57 g., and benzyl alcohol, 6.43 g., were treated as in Example 4. Methyl azelaaldehydate, 2.89 g., was obtained representin g a 97 percent yield.

Example 8 Soybean oil mixed methyl esters, 11.46 g. (46.96 meq. of C=C), n-butyl alcohol 20.0 g., and propionic acid 20.0 g. were treated as in Example 3 excepting that the hydrogenation took 1 hour. The mixed w-formyl ester product corresponded to a carbonyl yield of 97 percent.

It is pointed out that the instant invention is not to be confused. with that of Anders et al., application S.N. 453,525, filed of even date herewith and assigned to a common assignee, which copending application teaches an improved process for converting the known w-formyl ester products of the instant invention to nylon-forming precondensates.

I claim:

1. A process for obtaining substantially theoretical yields of methyl azelaaldehydate comprising:

(a) forming a reaction mixture consisting of methyl oleate and per part by weight thereof, about 1 to 10 parts by weight of an organic acid selected from the group consisting of acetic acid, glacial acetic acid, and propionic acid and, based on the weight of the organic acid component, about an equimolar quantity of an alcohol selected from the group consisting of ethnaol, propanol, butanol, Z-methoxyethanol, cyclohexyl alcohol, and benzyl alcohol;

(b) bubbling ozone-containing oxygen through the stirred reaction mixture until the theoretical amount of ozone is absorbed;

(c) bubbling hydrogenthrough the ozonized reaction mixture in the presence of palladium catalyst until reduction is essentially complete;

(d) forming a washable solution of the filtered and neutralized reaction mixture in a volatile solvent member selected fromthe group consisting of methylene chloride and diethyl ether;

(e) washing the solvent solution, and

(f) distilling the washed solution under reduced pressure to obtain methyl azelaaldehydate -in yields of not less than about 92 percent of theory. 2. The process of claim 1 wherein the organic acid is glacial acetic acid and the alcohol is ethanol.

References Citedv UNITED STATES PATENTS 2,820,046 1/1958 MacKenzie et a1. 260406 ALEX MAZEL, Primary Examiner.

R. GALLAGHER, Assistant Examiner. 

1. A PROCESS FOR OBTAINING SUBSTANTIALLY THEORETICAL YIELDS OF METHYL AZELAALDEHYDATE COMPRISING: (A) FORMING A REACTION MIXTURE CONSISTING OF METHYL OLEATE AND PER PART BY WEIGHT THEREOF, ABOUT 1 TO 10 PARTS BY WEIGHT OF AN ORGANIC ACID SELECTED FROM THE GROUP CONSISTING OF ACETIC ACID, GLACIAL ACETIC ACID, AND PROPIONIC ACID AND, BASED ON THE WEIGHT OF THE ORGANIC ACID COMPONENT, ABOUT AN EQUIMOLAR QUANTITY OF AN ALCOHOL SELECTED FROM THE GROUP CONSISTING OF ETHNAOL, PROPANOL, BUTANOL, 2-METHOXYETHANOL, CYCLOHEXYL ALCOHOL, AND BENZYL ALCOHOL; (B) BUBBLING OZONE-CONTAINING OXYGEN THROUGH THE STIRRED REACTION MIXTURE UNTIL THE THEORETICAL AMOUNT OF OZONE IS ABSORBED; (C) BUBBLING HYDROGEN THROUGH THE OZONIZED REACTION MIXTURE IN THE PRESENCE OF PALLADIUM CATALYST UNTIL REDUCTION IS ESSENTIALLY COMPLETE; (D) FORMING A WASHABLE SOLUTION OF THE FILTERED AND NEUTRALIZED REACTION MIXTURE IN A VOLATILE SOLVENT MEMBER SELECTED FROM THE GROUP CONSISTING OF METHYLENE CHLORIDE AND DIETHYL ETHER; (E) WASHING THE SOLVENT SOLUTION, AND (F) DISTILLING THE WASHED SOLUTION UNDER REDUCED PRESSURE TO OBTAIN METHYL AZELAALDEHYDATE IN YIELDS OF NOT LESS THAN ABOUT 92 PERCENT OF THEORY. 